7728321 has 4 divisors (see below), whose sum is σ = 10304432. Its totient is φ = 5152212.

The previous prime is 7728317. The next prime is 7728337. The reversal of 7728321 is 1238277.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 7728321 - 2² = 7728317 is a prime.

It is a Duffinian number.

7728321 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (7728311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1288051 + ... + 1288056.

It is an arithmetic number, because the mean of its divisors is an integer number (2576108).

Almost surely, 2^7728321 is an apocalyptic number.

It is an amenable number.

7728321 is a deficient number, since it is larger than the sum of its proper divisors (2576111).

7728321 is a wasteful number, since it uses less digits than its factorization.

7728321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2576110.

The product of its digits is 4704, while the sum is 30.

The square root of 7728321 is about 2779.9857913306. The cubic root of 7728321 is about 197.7098852965.

The spelling of 7728321 in words is "seven million, seven hundred twenty-eight thousand, three hundred twenty-one".